About foods, drinks and medical supplies and so on, the quality thereof is deteriorated by oxygen. They are therefore required to be stored in the absence of oxygen or under a condition that the oxygen content is very small.
For this reason, nitrogen may be filled into a container or a package for storing foods, drinks, medical supplies or the like. However, for example, there arises a problem that costs increase in the production thereof, or a problem that once the container is opened or the package is unwrapped, air flows thereinto from the outside, whereby the quality cannot be subsequently prevented from deterioration. Accordingly, various studies have been made for absorbing oxygen remaining into a container or package and removing the oxygen from the system.
Conventionally, as the method for removing oxygen in a container or a package, there has widely been performed a method of arranging there in a different small bag in which an oxygen absorber made mainly of iron powder is included. However, according to this method, inconveniences are generated in the case where a metal detector is used to detect an alien substance or in the case of cocking or warming something to eat or drink in an microwave oven although this method is economical and gives a large oxygen absorbing rate.
Thus, about container or packaging materials made of resin, studies have been made for causing the container or packaging materials themselves to have oxygen-absorbing ability.
Suggested is, for example, the use of an oxygen absorber containing a polyterpene such as poly(α-pinene) poly(β-pinene) or poly(dipentene) and a transition metal salt, which acts as an oxygen absorbing catalyst, such as cobalt neodecanoate or cobalt oleate (Patent Document 1).
Suggested is also the use of an oxygen absorber containing a conjugated diene polymer, such as polyisoprene or 1,2-polybutadiene, and a transition metal salt (Patent Document 2)
Furthermore, suggested is the use of an oxygen absorber containing a copolymer made from ethylene and cyclopentene, and a transition metal salt (Patent Document 3).
However, about these oxygen absorbers in the prior art, with the advance of oxygen absorbing reaction, the polymer therein may deteriorate so as to decrease the mechanical strength remarkably, or the transition metal salt may elute out. Therefore, the conventional oxygen absorbers cannot be adopted in accordance with the usage thereof.    Patent Document 1: Japanese Patent Application National Publication (Laid-Open) No. 2001-507045    Patent Document 2: Japanese Patent Application Laid-Open No. 2003-71992    Patent Document 3: Japanese Patent Application National Publication (Laid-Open) No. 2003-504042